Praxair will team with Georgia Institute of Technology (Georgia Tech) to perform bench-scale testing of a sub-ambient air separation process based on a rapidly cycled pressure swing adsorption (RCPSA) system that removes a bottleneck from a traditional cryogenic air separation unit. Hollow fiber-sorbent contactors will be used for the sorbent materials. On the lab scale, these have been shown to be 3 to5 times more productive than traditional adsorbent contactors and have a pressure drop 3 to 5 times less than that of standard contactors. A key feature of this process is the ability to perform efficient heat integration, enabling recovery of much of the energy required for gas cooling. One of the key goals of this project is to determine the optimum process structure. Researchers will fabricate hollow fiber contactors and generate sub-ambient isotherms for these materials. They will also perform RCPSA experiments on the fibers and assess the efficacy of an internal phase change material. The RCPSA experimental results will be incorporated into a process model that feeds into a detailed techno-economic assessment. A large prototype module of approximately 100 fibers will be tested to provide insight into module scale-up. Praxair will manage the project and lead the techno-economic analysis. Georgia Tech will perform the fiber spinning and RCPSA experimental work.

Project Benefits

Traditional adsorption air separation units using beaded adsorbents struggle to compete with the better cost and productivity of cryogenic distillation systems. Praxair intends to overcome factors that limit performance by combining the advantages of a heat integrated, compact, and energy efficient hollow fiber pressure swing adsorption system with those of sub-ambient separations. Hollow fiber sorbents have been demonstrated to be 3 to 5 times more capital and energy efficient than traditional bead-packed fixed beds for certain applications. It is envisioned that this advantage, coupled with the performance gains from operating at sub-ambient temperatures, will make large-scale adsorptive air separation technology economically attractive.